<style>
    #form-modal{
        top: 20%;
        margin-top: 0px !important;
    }
</style>

<div id="form-modal" class="modal hide fade modal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
    <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
        <h3 id="myModalLabel">
            Modal Header
        </h3>
    </div>
    <div class="modal-body">
        Modal Body
    </div>
</div>